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Have you ever seen the Virgin Mary in your grilled cheese? Or a screaming face inside a bell pepper? Seeing faces in inanimate objects is a common phenomenon. Now it seems that we’re not alone in experiencing it – monkeys do too.
Pareidolia is the scientific term for erroneously perceiving faces where none exist. Other examples including seeing “ghosts” in blurry photos and the man in the moon.
To investigate whether pareidolia was a uniquely human experience, Jessica Taubert at the US National Institute of Mental Health in Maryland and her colleagues trained five rhesus macaques to stare at pairs of photos.
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Each photo showed either an inanimate object that prompts pareidolia in humans, an equivalent object that doesn’t, or the face of a monkey (below).
Current Biology
We already knew that both people and monkeys will look longer at images of faces than other things. So the team presented each of the photos in every possible pairing – 1980 in all – and measured the time the monkeys spent looking at each.
The monkeys did indeed seem to succumb to pareidolia – they spent more time looking at illusory faces than the non-illusory photos they were paired with.
Interestingly, they also spent more time looking at the illusory faces than the monkey faces, perhaps because they spent longer studying these more unusual “faces”, or because they tend to dislike holding the gaze of another monkey.
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Examining the eye gaze patterns of the monkeys, the team found that they frequently fixated on the “eye” and “mouth” regions of the false faces, which is also how people behave when viewing real faces.
Vincent Reid, a psychologist at Lancaster University, UK, says he is not surprised by the finding because rhesus monkeys are very social animals. “Just like humans, they rely on facial information for communicative purposes.”
But why do we – and monkeys – so often perceive faces where there are none?
Our brain is primed to see faces from an early age. Babies can recognise a face while still in the womb – scans show that when dots of light are shone through the skin, fetuses preferentially turn to look at patterns that resemble faces, but ignore random shapes.
Being able to quickly spot and interpret a face can give vital information about whether a social group is friendly or hostile. But sometimes we are too good at spotting faces, seeing Jesus in a jar of Marmite.
The fact that monkeys also easily perceive false faces underscores the biological advantage for social animals to preferentially detect faces in the environment. “It shows how deeply engrained it is in humans,” says Reid.
Journal reference: Current Biology, DOI: 10.1016/j.cub.2017.06.075
Read more: Our knack for remembering faces is a highly evolved skill
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